Method and apparatus for supplying gas under pressure



May 7, 1968 H. D. NETTLES 3,381,523 I METHOD AND APPARATUS FOR SUPPLYING GAS UNDER PRESSURE Filed March 3, 1965 United States Patent 3,381,523 METHOD AND APPARATUS FOR SUPPLYING GAS UNDER PRESSURE Henry D. Nettles, 1806 Swan St., Longview, Tex. 75601 Filed Mar. 3, 1965, Ser. No. 436,741 14 Claims. (Cl. 7340.5)

ABSTRACT OF THE DISCLOSURE A method and apparatus for supplying gaseous carbon dioxide to a wellhead in communication with an oil reservoir or the like, including a portable generator tank preferably mounted on a truck or other vehicle, a heating jacket surrounding the tank and adapted to receive a heating fluid at least in the lower part of the jacket, a heating element such as an electrical heating element or means for circulating hot water from a truck radiator or the radiator of another engine through the heating jacket, a carbon dioxide introduction system connected to the carbon dioxide generating tank, including a first valve adapted to pass a solid stick of carbon dioxide into a holding pipe or chamber and a second valve mounted below the chamber and adapted to pass the solid stick of carbon dioxide from the chamber into the generating tank, a gaseous carbon dioxide outlet connected to the vapor space of the generating tank and a gaseous carbon dioxide line leading from the carbon dioxide outlet to the wellhead. A pressure relief valve may also be mounted on the generating tank as well as a pressure gauge. A valve and pressure gauge may also be mounted in the line leading to the Wellhead. One method of utilizing the apparatus in oil field operations is to apply the gaseous carbon dioxide to one side of the piece of well equipment, such as a casing and then observe any leakage of carbon dioxide to the opposite side of the casing.

been used as a source of pressure to fracture a subsurface formation and thereby increase its permeability to fluids. For such operations, relatively small amounts of gas are utilized at pressures in the neighborhood of 500 to 3500 p.s.i. In other operations, such as the displacement of oil from subsurface reservoirs, both liquids and gases have been used individually and in various combinations. While most such secondary recovery operations require very substantial volumes of gas, there are certain operations of this character where a liquid can be aerated or foamed with a gas and thus produce an effective displacement medium having many of the advantages of gas displacement while using only limited amounts of gas. Aerated or foamed liquids have also been used in treating subsurface formations with acid to increase the permeability, as paraflin solvents to dissolve paraflin deposits from subsurface formations and well equipment, as surfactants or detergents for various formation and equipment cleaning purposes, as corrosion inhibitors, as fracturing fluids, etc. There is also a need in oil field operations for techniques and means for pressure testing various items of equipment at the well location, such as,

3,381,523 Patented May 7, 1968 threaded joints of piping utilized in the control of the well and in the production of oil and other fluids from the subsurface formation to the surface of the earth. Certain types of fluid pumps and valves used in oil field operations also can be operated by gases under pressure; and devices such as packers and blow-out preventers, designed to seal a conduit against fluid transmission, are often fluid-expandable and can be conveniently operated by gases under pressure.

While a number of gases are available for use in the above-mentioned operations, a number of these gases are flammable, and thus present a hazard. For example, natural gas is readily available but is highly flammable and, when compressed, represents an explosive mixture. Likewise, normally gaseous hydrocarbon materials, such as, propane and butane, have been liquefied and utilized in a liquefied or gaseous state in various oil field operations. However, these materials are also flammable and explosive under the conditions of use encountered; and, therefore, great care is required in the handling of these materials. Another gas which has been suggested for use in both the gaseous and the liquefied form is nitrogen. Nitrogen in its essentially pure form, as opposed to its combination in air, is relatively inert and thus can be handled without the dangers incident in the use of flammable gases. However, nitrogen is not readily available. In addition, the liquefication of nitrogen requires the application of extremely high pressures in order to maintain the material in its liquid form so that extensive compression and/or cooling equipment must be available at the site of use or the liquefied nitrogen must be transported to the site in special high pressure vessels. Carbon dioxide, on the other hand, is a readily available and effective material for use in oil field operations, particularly because of its non-flammability. Also, carbon dioxide is non-corrosive and thus does not contribute to the very severe corrosion problems normally encountered in oil field operations. In addition, carbon dioxide has a critical temperature of about 88 F. and therefore can be liquefied and maintained in a liquid condition at a comparatively low pressure, the vapor pressure at the critical temperature being about 1,070 p.s.i. Accordingly, the use of liquefied carbon dioxide for certain of the above-mentioned oil field operations has been suggested. However, as is the case in the use of liquefied nitrogen, the use of liquefied carbon dioxide requires either the provision of rather expensive compression and/or cooling equipment at the well location, or the transport of the liquefied material in special containers, the only difference being that the transport container need not be capable of withstanding as high a pressure as is required for nitrogen. Accordingly, it is obvious that there is no present technique or equipment for readily supplying relatively small amounts of gases under pressure for use in oil field operations at remote well locations. Specifically, there is a great need for a simple and convenient method and means for supplying limited quantities of non-explosive gases under relatively low pressures for the testing and operation of oil field equipment and the conduct of oil field operations.

It is therefore an object of the present invention to provide an improved method and apparatus for supplying gas under pressure.

Another object of the present invention is to provide an improved method and apparatus for supplying gas under pressure to oil field operations.

Still another object of the present invention is to provide an improved method and apparatus for supplying gas under pressure to a well head located on. a well leading to subsurface petroliferous deposits.

A further object of the present invention is to provide 3 an improved method and apparatus -.for pressure testing oil field equipment.

Another and further object of the present invention is to provide an improved method and apparatus for pressure testing joints in pipes used in oil wells.

Yet another object of the present invention is to provide an improved method and apparatus for supplying gaseous carbon dioxide under pressure.

A still further object of the present invention is to provide an improved apparatus for supplying gaseous carbon dioxide under pressure wherein solid carbon dioxide is readily converted to its gaseous form.

Another and further object of the present invention is to provide an improved apparatus for supplying carbon dioxide under pressure which includes improved means for introducing solid carbon dioxide to a tank in which it is converted to its gaseous form.

Still another object of the present invention is to provide an improved high pressure vessel and method of manufacturing the same.

These and other objects and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the drawing wherein:

The drawing is a side elevational view, partially in section, of the apparatus of the present invention in use at a well site.

In accordance with the drawing, the portable gas pressure source is mounted on a suitable transport vehicle 10. Transport vehicle may be a flat-bed truck, as shown in the drawing, a panel truck, a trailer, or other motive means 'for readily moving the pressure source from one well location to another. As previously indicated, gas under pressure is supplied from the portable source to a well head '12, where it is utilized in many and varied oil field operations. As illustrated in the drawing, well head 12 is attached to the top of a large casing 14, which is disposed in a well drilled into the earth. A smaller pipe or tubing 16 is shown being inserted into the well through the well head and thence into casing 14. Accordingly, in the illustrated use the portable gas pressure source of the present invention is being utilized to pressure test the joints of tubing 16. High pressure vessel 18 is shown mounted on appropriate supports 20 within a low pressure vessel 22. Low pressure vessel 22 is supplied with liquid through liquid inlet line 24 and discharges liquid through liquid outlet line 26. In the embodiment shown, inlet line 24 and outlet line 26 pass to the radiator 28 of truck 10 and lines 24 and 26 therefore serve as conduits for the circulation of hot Water from radiator 28 through low pressure vessel 22. While normally conventional flow and the water pump of truck 10 will supply the necessary energy to circulate the hot water, it may be desirable in some cases to provide a booster pump on either of lines 24 or 26. Fluid lines 24 and 26 are also preferably flexible hoses and are detachable from radiator 28. This will permit the hoses to be connected to the radiator of any appropriate internal combustion engine at the well location. In many instances, there is available at the well head a suitable internal combustion engine utilized as a prime mover for some unit of equipment and this engine can be used to supply hot water to low pressure vessel 22. An alternative means of heating the liquid contained in low pressure vessel 22 is shown as electrical heating coil 30, which is disposed in low pressure vessel 22. Heating coil 30 may be any appropriate resistance-type heating coil having connected thereto power lines 32 which may be connected to a suitable source of power. Accordingly, the fluid contained with in low pressure vessel 22 may be heated electrically where an appropriate source of electric power is available at the well site. Other sources of heat, such as a direct gas heater or a gas heater utilized to heat circulating water, may also be utilized. The significant point is that very little heat is required, because of the low sublimation temperature of carbon dioxide, and the prescut portable gas pressure source is therefore adaptable to use in any remote Well location to supply gas under pressure. The portable gas pressure source of the present invention may also be readily removed from the transport vehicle because of its light weight, small size and the utilization of flexible hoses 24 and 26. For this purpose, loop-type handles 34 are welded to the ends of high pressure vessel 18 and pass outwardly through low pressure vessel 22. Mounted in the top of high pressure vessel 18 is upstanding charging pipe 36. Pipe 36 passes through low pressure vessel 22 and is exposed outside vessel 22 where it will be readily accessible to the operator. Pipe 36 is provided with lower valve 38 and upper valve '40. Valves 38 and 40 are appropriate gate-type valves and the utilization and importance of charging pipe 36 and valves 38 and 40 will be pointed out hereinafter in the description of the operation of the apparatus. Also attached to high pressure vessel 18 and in open communication therewith is a pressure relief valve 42. Relief valve 42 is what is commonly referred to as a pop valve and, depending upon the desired internal pressure to be maintained in vessel 18, pop valve 42 will operate to open and relieve the pressure when it exceeds the preselected pressure and automatically close when the pressure has been relieved and the preselected pressure in vessel 18 has again been attained. Such operation of pop valve 42 will occur rather frequently but it is not necessary that the valve remain open any length of time in order to maintain a safe pressure in vessel 18. Also in communication with vessel 18 is main pressure gauge 44. An appropriate valve 46 is mounted in line 48 leading from the interior of high pressure vessel 18 to pressure gauge 44. When it is desired to monitor the pressure in high pressure vessel 18, valve 46 will be opened, otherwise valve 46 may remain closed without altering the operation of the present apparatus. Gas is supplied to well head unit 12 from high pressure vessel 18 through gas line section 50. Gas line section 54 is provided with shut off valve 52 adapted to open and close the supply line as desired. Gas line section 50 is preterably a flexible hose and therefore an appropriate metallic gas line section 54 is utilized for the mounting of valve 52. Also in gas line section 54 is mounted an appropriate pressure gauge 56. Pressure gauge 56 is adapted to measure the pressure of the gas actually being supplied to well head '12 and will be utilized at all times when gas under pressure is being supplied to the well head. An appropriate valve 58 is mounted between gauge 56 and line 54 to interrupt the flow of gas to gauge 56 when desired. High pressure vessel 18 is also supplied with a drain valve 60 for the discharge of condensed water, etc., which may accumulate in vessel 18 from time to time.

The high pressure vessel 18 is also relatively inexpensive and unique in construction. In oil field operations large metallic pipes, capable of withstanding extremely high pressures without rupture, are utilized to case a well and serve as a conduit for the production of fluids. This casing can be obtained either in a seamless or seamed structure. Accordingly, a length of this metallic high testpressure casing can be utilized in the construction of high pressure vessel 18 and is ideally suited for this purpose. Vessel 18 is constructed by cutting a length of high testpressure pipe to the desired ultimate length of the vessel and thereafter cutting generally V-shaped sections from opposing sides of both ends of this elongated section of pipe. A second section of the same cylindrical pipe generally equal in length to the diameter of the pipe is then cut and a pair of curved generally diamond-shaped sections are cut from the sides of this section of pipe transverse to its length. These diamond-shaped, curved sections are then welded in place in the V-shaped notches formed in the elongated section of pipe to thereby close the ends of the elongated section of pipe and form an appropriate high pressure vessel.

Solid carbon dioxide for use in accordance with the present invention is readily available and may be ob tained in the form of elongated sticks. In the use of the present apparatus, the apparatus is transported to the desired well site by an appropriate vehicle. A supply of solid carbon dioxide is fed to high pressure vessel 18 by closing valve 38 and opening valve 40 and inserting a stick of solid carbon dioxide in chamber 36 between the two valves. Thereafter, valve 40 is closed and valve 38 opened to drop the solid carbon dioxide into vessel 18. This procedure is repeated during the use of the apparatus, and, accordingly, solid carbon dioxide may be added to replenish the supply in vessel 18 without interrupting the operation being carried out, since the inlet means permits one to maintain the vessel closed to the atmosphere at all times during charging of solid carbon dioxide. After the vessel 18 has been charged with suiiicient solid car- 'bon dioxide, heat is applied to the fluid contained in low pressure vessel 22, either by activating electrical heating element 30 or by connecting lines 24 and 26 to the radiator of an internal combustion engine, such as, the engine of the vehicle used to transport the equipment. The hot water in the cooling system of the Vehicle is then circulated through vessel 22. Where the radiator of an internal combustion engine is not employed to supply hot water to vessel 22, fluids other than water may be disposed in vessel 22 and usedas a heating medium. For example, kerosene or other suitable liquids may be utilized and these fluids may be electrically heated as by coil 30, or by a gas jet, either directly or indirectly. Such gas heating is convenient, since in most cases natural gas is available at the well location. It is also possible to circulate steam through vessel 22 if a suitable source of steam is available. Pop valve 42 is set at the desired pressure which is to be maintained within vessel 18 and which is to be supplied for use in the well operation and, to the extent that the pressure exceeds the set pressure, the pop valve will intermittently operate to relieve the excess pressure and maintain the pressure below the preselected pressure. Valve 46 is opened at the outset of the operation so that the pressure within vessel 38 may be observed on pressure gauge 44. When the pressure has attained the preselected value, as observed on gauge 44, line 50 is connected to an appropriate connection on well head 12 and valve 52 is open to supply gaseous carbon dioxide to well head 12. While gaseous carbon dioxide is being supplied to well head 12, valve 58 may be opened and gauge 56 utilized to monitor pressure in the supply line. As shown in the drawing, the gaseous carbon dioxide is being utilized to pressure test a string of tubing 16 being inserted through well head 12 and casing 14 into the well. By applying gaseous carbon dioxide under pressure to the outside of tubing 16, leaks in the joints of tubing 16 or in the tubing itself may be detected. Various means of detection may be employed. Normally, orifice-type leaks of the character generally encountered can be readily detected, since the leakage of the high pressure gas through the orifice-type opening will create an audible sound. A leak may also be detected by observing a sudden pressure drop in the supply line to the well head or a sudden pressure increase in the interior of tubing 16.

As previously indicated, the apparatus of the present invention provides a mobile, inexpensive source of gas under pressure for a wide variety of oil field operations which may be readily utilized at remote locations where it is too expensive, impossible or inconvenient to obtain suitable pressurized gases. Variations and modifications other than those specifically set forth herein by way of example will occur to one skilled in the art. Accordingly, the present invention is to be limited only in accordance. with the appended claims.

I claim:

1. A mobile apparatus for supplying carbon dioxide for oil field operations at a pressure above atmospheric pressure, comprising:

(a) a vehicle adapted to be moved from one location to another;

(b) a first vessel, adapted to receive a liquid, mounted on said vehicle;

(c) an internal combustion engine having a cooling system containing a circulating liquid;

(d) liquid feed lines leading from said cooling systern to said vessel and back to said cooling system for circulating hot liquid from said cooling system through said first vessel and back to said cooling system;

(e) a second vessel, adapted to withstand a preselected pressure above atmospheric pressure, mounted within said first vessel and at least partially submerged in liquid disposed in said first vessel;

(f) a vertically-disposed, elongated pipe mounted on the top of said second vessel and in open communication therewith;

(g) first valve means mounted in said pipe adjacent said second vessel;

(h) second valve means mounted in said pipe a sufficient distance above said first valve means to form a receiving chamber of sufficient length to temporarily accommodate pieces of solid carbon dioxide;

(i) a pressure regulator valve, adapted to maintain a substantially constant pressure within said second vessel, mounted on said second vessel and in open communication therewith;

(j) a first pressure gauge means mounted on said second vessel and in open communication therewith;

(k) well head means connected to the point of use of the pressurized carbon dioxide;

(1) a carbon dioxide supply line leading from the vapor space of said second vessel to said well head means;

(m) valve means mounted in said supply line and in open communication therewith; and

(n) a second pressure gauge means mounted in said supply line and in open communication therewith.

2. Apparatus in accordance with claim 1 wherein the internal combustion engine is also the .motive power for the vehicle.

3. Apparatus in accordance with claim 1 which additionally includes an electrically operated heating element disposed in the fluid contained in the first vesse 4. Apparatus for supplying carbon dioxide for oil field operations at a pressure above atmospheric pressure to a Well head, comprising:

(a) a vessel adapted to withstand pressures above atmospheric pressure;

(b) inlet means communicating with the top of said vessel and including a first valve means adapted to pass solid carbon dioxide therethrough and into said vessel, adjacent said vessel and a second valve means adapted to pass solid car-hon dioxide therethrough spaced a sufiicient distance above said first valve means to form a chamber adapted to temporarily accommodate pieces of solid carbon dioxide;

(0) heating means for applying heat to said vessel to raise the temperature within said vessel above atmospheric temperature;

((1) gas outlet means communicating with the gas space of said vessel; and

(e) a carbon dioxide supply line means leading from said gas outlet means to a well head in communication with a well in the oil field.

5. Apparatus in accordance with claim 4 wherein the vessel is formed from a high test-pressure, metallic pipe.

6. Apparatus in accordance with claim 4 wherein the inlet means is a vertically disposed pipe having the first and second valve means mounted therein at spaced points.

7. Apparatus in accordance with claim 4 wherein the first and second valve means are gate-type valves.

8. Apparatus in accordance with claim 4 wherein the first vessel is mounted within a second vessel adapted to maintain a body of liquid about at least a part of said first vessel.

9. Apparatus in accordance with claim 8 which includes means for circulating a hot liquid through the second vessel.

10. Apparatus in accordance with claim 8 which includes an internal combustion engine having a cooling system containing a circulating liquid and said cooling system is connected to the second vessel in a manner to circulate said liquid through said second vessel,

11. Apparatus in accordance with claim 8 which includes an electrical heating means disposed in a body of liquid in said second vessel.

12. Apparatus in accordance with claim 8 which includes an electrical heating means disposed in a body of liquid in the second vessel and means for circulating a hot liquid through said second vessel.

13. A method of pressure-testing an item of equipment designed to Withstand a substantial pressure differential on either side of the same, comprising:

(a) periodically introducing solid carbon dioxide to a vessel adapted to withstand pressures above atmospheric by closing an inlet immediately adjacent said vessel, introducing the solid carbon dioxide into a chamber immediately above said inlet, closing said inlet to said chamber, and thereafter opening said inlet immediately adjacent said vessel to permit said solid carbon dioxide to drop into said vessel from said chamber;

(b) heating said vessel to an elevated temperature above atmospheric temperature and suflicient to gasify said solid carbon dioxide; and

(c) applying the pressure of said gasified carbon dioxide to one side of the item of equipment being Cir tested in a manner to permit the observance of the passage of carbon dioxide through said piece of equipment from said one side to the opposite side.

14. A method of pressure-testing an item of equipment designed to withstand a substantial pressure differential on either side of the same, comprising:

(a) periodically introducing solid carbon dioxide to a vessel adapted to withstand pressures above atmospheric pressure;

(b) heating said vessel to an elevated temperature above atmospheric temperature and sufficient to gasify said solid carbon dioxide by circulating heated cooling liquid from a liquid-cooled internal combustion engine about said vessel; and

(c) applying the pressure of the said gasified carbon dioxide to one side of the item of equipment being tested in a manner to permit the observance of the passage of carbon dioxide through said piece of equipment from one side to the opposite side.

References Cited UNITED STATES PATENTS 1,785,326 12/1930 Rudd 6246 X 1,908,290 5/1933 Goosmann 62-46 X 1,972,771 9/1934 Haid et al 6246 2,516,218 7/1950 Ker-r 62-52 2,875,833 3/1959 Martin 166--9 3,100,528 8/1963 Plummer et al 16642 X LOUIS R. PRINCE, Primary Examiner.

I, NOLTON, Assistant Examiner. 

